Validation and performance of a rapid HIV-1 viral load assay
4 affiliations
- 1Johns Hopkins Hospital Medical Microbiology Laboratory, Baltimore, Maryland, USA
- 2Division of Infectious Disease, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
- 3Centers for Disease Control and Prevention, Atlanta, Georgia, USA
- 4Division of Medical Microbiology, Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
Abstract
Current diagnostic algorithms for HIV-1 primarily depend on antigen-antibody tests, with nucleic acid tests reserved for confirmation and monitoring of antiretroviral therapy. Incorporating a quantitative nucleic acid test at the point of care could provide faster diagnosis and viral load measurement in a single clinical encounter, expediting linkage to care. This study evaluates the Xpert HIV-1 Viral Load XC (Xpert VL XC) assay as a candidate for primary nucleic acid testing use within HIV-1 diagnostic workflows, compared to standard-of-care approaches. The Xpert VL XC demonstrated a measurable analytical range of 60–1 × 106 copies/mL (R2 = 0.99) with 100% detection across tested concentrations. Precision analyses showed greatest variability at the lowest concentration, with acceptable assay reproducibility. Agreement analyses using 20 HIV-1 positive and 10 HIV-1 negative plasma samples showed 100% agreement compared to the Roche cobas HIV-1 (quantitative) assay. The Xpert VL XC was compared to four other HIV assays, including the Xpert HIV-1 Qual XC. The Xpert VL XC produced 3.2% invalid results and achieved negative agreement of ≥96.8%. Positive agreement ranged from 80.8% to 90.0%, with most discrepancies occurring below the 40 copies/mL lower limit of quantification threshold. The Xpert HIV-1 Qual XC was the only assay that detected all 26 samples that were positive using the standard immunoassay diagnostic algorithm. Average turnaround time was 3 h, faster than the 21 h average for conventional batch testing. These findings highlight the limitations of implementing rapid molecular HIV-1 diagnostics and the need for both sensitive and rapid approaches.
IMPORTANCE: Current testing algorithms for the diagnosis of HIV-1 initially test samples with an antigen/antibody test followed by an antibody differentiation test if the screening test is positive. Nucleic acid tests are used to aid in the diagnosis (qualitative and quantitative assays) or monitoring a patient’s response to antiretroviral therapy (quantitative). However, a quantitative diagnostic nucleic acid test may have additional utility, particularly in point-of-care settings, or near the patient care site. This would allow both diagnosis and initial viral load measurement to occur during a single visit, permitting rapid linkage to care. We evaluated the Xpert HIV-1 Viral Load XC test as a potential tool for primary nucleic acid testing within the HIV-1 diagnostic algorithm and assessed its suitability for use under the unique constraints of point-of-care environments.
Related
- An optimized product-enhanced reverse transcriptase assay for sensitive and quantitative detection of HIV viral load and phenotypic drug resistance
- Quantification by Real-Time PCR Assay of Staphylococcus aureus Load: a Useful Tool for Rapidly Identifying Persistent Nasal Carriers
- Torque Teno Virus Viremia in Complicated Staphylococcus aureus Infection: Prevalence, Viral Load, and Associations With Inflammatory Markers and Clinical Outcomes
- High Mortality in Adults With Community-Acquired Pneumonia Admitted to Hospitals in South Africa Before and During the COVID-19 Pandemic, Stratified by HIV Serostatus and Viral Load: Data From a Prospective Cohort Study (2019–2021)
- Effect of a mHealth intervention on detectable HIV-1 viral load: a remote randomised controlled trial
BibTeX
@article{uhteg2026validation,
title = {{Validation and performance of a rapid HIV-1 viral load assay}},
author = {Katharine Uhteg and Mohammad H. Bayan and Alec Boudreau and Zoe O. Demko and Robin J. MacGowan and Kevin P. Delaney and Yukari C. Manabe and Matthew M. Hamill and Heba H. Mostafa},
journal = {Microbiology Spectrum},
year = {2026},
month = sep,
doi = {10.1128/spectrum.02646-26},
url = {https://doi.org/10.1128/spectrum.02646-26},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Validation and performance of a rapid HIV-1 viral load assay
AU - Katharine Uhteg
AU - Mohammad H. Bayan
AU - Alec Boudreau
AU - Zoe O. Demko
AU - Robin J. MacGowan
AU - Kevin P. Delaney
AU - Yukari C. Manabe
AU - Matthew M. Hamill
AU - Heba H. Mostafa
PY - 2026
DA - 2026/09/23
JO - Microbiology Spectrum
DO - 10.1128/spectrum.02646-26
UR - https://doi.org/10.1128/spectrum.02646-26
AB - Current diagnostic algorithms for HIV-1 primarily depend on antigen-antibody tests, with nucleic acid tests reserved for confirmation and monitoring of antiretroviral therapy. Incorporating a quantitative nucleic acid test at the point of care could provide faster diagnosis and viral load measurement in a single clinical encounter, expediting linkage to care. This study evaluates the Xpert HIV-1 Viral Load XC (Xpert VL XC) assay as a candidate for primary nucleic acid testing use within HIV-1 diagnostic workflows, compared to standard-of-care approaches. The Xpert VL XC demonstrated a measurable analytical range of 60–1 × 106 copies/mL (R2 = 0.99) with 100% detection across tested concentrations. Precision analyses showed greatest variability at the lowest concentration, with acceptable assay reproducibility. Agreement analyses using 20 HIV-1 positive and 10 HIV-1 negative plasma samples showed 100% agreement compared to the Roche cobas HIV-1 (quantitative) assay. The Xpert VL XC was compared to four other HIV assays, including the Xpert HIV-1 Qual XC. The Xpert VL XC produced 3.2% invalid results and achieved negative agreement of ≥96.8%. Positive agreement ranged from 80.8% to 90.0%, with most discrepancies occurring below the 40 copies/mL lower limit of quantification threshold. The Xpert HIV-1 Qual XC was the only assay that detected all 26 samples that were positive using the standard immunoassay diagnostic algorithm. Average turnaround time was 3 h, faster than the 21 h average for conventional batch testing. These findings highlight the limitations of implementing rapid molecular HIV-1 diagnostics and the need for both sensitive and rapid approaches. IMPORTANCE: Current testing algorithms for the diagnosis of HIV-1 initially test samples with an antigen/antibody test followed by an antibody differentiation test if the screening test is positive. Nucleic acid tests are used to aid in the diagnosis (qualitative and quantitative assays) or monitoring a patient’s response to antiretroviral therapy (quantitative). However, a quantitative diagnostic nucleic acid test may have additional utility, particularly in point-of-care settings, or near the patient care site. This would allow both diagnosis and initial viral load measurement to occur during a single visit, permitting rapid linkage to care. We evaluated the Xpert HIV-1 Viral Load XC test as a potential tool for primary nucleic acid testing within the HIV-1 diagnostic algorithm and assessed its suitability for use under the unique constraints of point-of-care environments.
SN - 2165-0497
ER -